en 23926567 Background: Nowadays, Chlamydia trachomatis is known as a causative agent of infertility. Because of, asymptomatic nature of infection, many may suffer from its lasting complications such as infertility. This study was performed in Tehran during April 2007 to April 2008 to compare the prevalence of Chlamydia trachomatis infection in fertile and infertile women using ELISA and PCR methods. Methods: Overall, 234 infertile and 223 pregnant women, as the fertile group, participated in this hospital-based case-control study. After completing an informed consent form and the questionnaire, first catch urine and blood sample were obtained for PCR and ELISA (IgG, IgM) tests, respectively. Logistic regression analysis was used to control possible confounding factors, and determine adjusted odds ratio of infertility due to the infection. Results: PCR results revealed that 29 (12.4%) of the infertile and 19 (8.5%) of the fertile women were positive for C. trachomatis infection (p=0.440). IgG was positive in 21 (9.0%) of the infertile and 11 (5.0%) in the fertile group (p=0.093). IgM assays identified that 2 (0.9%) of the infertile and 4 (1.8%) of the fertile women were positive for the micro-organism (p=0.375). Conclusion: We found no significant differences among fertile and infertile women for Chlamydia trachomatis infection. Nevertheless, molecular techniques which are more sensitive, more specific and non-invasive can be used to detect C. trachomatis infection. Case control study, Chlamydia trachomatis, Enzyme-linked immunosorbent assay, Infertility, Polymerase chain reaction 67 73 https://www.jri.ir/article/528 https://www.jri.ir/documents/fullpaper/en/528.pdf BatoolHossein RashidiVali-e- Asar Reproductive Health Research Center,Tehran Medical Sciences University, Tehran, Iranبتولحسين رشيدي186LeiliChamani TabrizInfectious Diseases and Tropical Medicine Research Center, Shahid Beheshti University of Medical Sciences, Tehran, Iranليليچمني تبریزlchamani@avicenna.ac.ir62FedyehHaghollahiVali-e- Asar Reproductive Health Research Center,Tehran Medical Sciences University, Tehran, Iranفدیهحق‌اللهی508MahmoodJeddi-TehraniMonoclonal Antibody Research Center, Avicenna Research Institute (ACECR), Tehran, Iranمحمود جدی‌تهرانی54Mohammad MehdiNaghizadehDepartment of Biostatistics and Epidemiology, Fassa University of Medical Sciences, Fasa, Iranمحمدمهدینقی زاده731MamakShariatMaternal-Fetal-Neonatal Health Research Center, Tehran University of Medical Sciences, Tehran, Iranمامکشریعت507Mohammad MehdiAkhondiReproductive Biotechnology Research Center, Avicenna Research Institute, ACECR, Tehran, Iranمحمدمهدیآخوندی21RezvanBagheriReproductive Biotechnology Research Center, Avicenna Research Institute, ACECR, Tehran, IranRezvanBagheri1105SoheilaAsgariInternational Campus, Tehran University of Medical Sciences, Kish Island, Iranسهيلاعسگري551KevanWylieConsultant in sexual Medicine, Sheffield, United KingdomKevanWylie1141